Evergreen, Stephanie, D.H., author
Sage, 2020
Buku Teks
Krum, Randy, author
John Wiley & Sons, 2014
Buku Teks
Rifza Putra Kurniawan, author
2010
UI - Skripsi (Open)
The World Bank, 2002
Buku Teks
Carroll, Phil
McGraw-Hill Book Company,INC, 1950
Buku Teks